Cupertino tax accountant for the equity-heavy household

Cupertino, CA · Updated May 2026 · 9 min read

If you work for a large Cupertino-headquartered tech employer, your tax return looks nothing like the IRS Form 1040 instructions imagine. You have a base salary that is the small part of your comp. You have quarterly RSU vests where your employer withholds 22% federal even though your marginal rate is 35% or 37%. You have an ESPP that runs on a six-month offering cycle with a 15% discount and a look-back, throwing off lots you're supposed to track on two separate clocks. And the stock that all of this is paid in has done well enough that more than half of your net worth is now in a single ticker. A Cupertino tax accountant who has never actually run the numbers on that combination will get the result wrong every April. Often by five figures.

The withholding gap nobody warns you about

This is the most common surprise we see in new Cupertino client intake meetings. Your employer's payroll system withholds federal supplemental tax at the IRS statutory flat rate of 22% on the first $1,000,000 of supplemental wages each calendar year, then 37% above that line (IRC §3402(o), Treas. Reg. §31.3402(g)-1). California adds 10.23% supplemental, plus Medicare and the 0.9% additional Medicare tax once you cross $200,000 of wages. For a senior engineer or principal architect with $250,000 base and $300,000 of RSU income, the gap between what was withheld and what you actually owe runs $25,000 to $45,000 per year on the federal side alone.

You will not feel it until April. By then it is too late to fix without owing underpayment penalties under IRC §6654. The fix is simple and we run it every quarter for our equity-comp clients:

1. Project full-year liability after each vest using actual YTD income.
2. Compare to YTD withholding plus estimates already paid.
3. Adjust W-4 step 4(c) (additional withholding per pay period) or wire a quarterly estimated payment to cover the gap.
4. Hit a safe harbor: pay at least 110% of last year's federal tax for AGI above $150,000, or 90% of current year. Either one stops penalty accrual cold.

For a deeper walk through the math of RSU withholding shortfalls, read our 2026 guide on RSU vesting and tax treatment.

ESPP timing: the two-clock problem

Every share you buy through an employee stock purchase plan starts two clocks the moment it is purchased. Clock one runs from the offering date (when the look-back price was locked in). Clock two runs from the purchase date (when you actually got the shares). To get the favorable "qualifying disposition" treatment under IRC §423, both clocks must show: more than two years from offering date AND more than one year from purchase date.

If you sell before both clocks ring, you have a "disqualifying disposition." The discount built into the purchase price (typically 15% off the lower of the offering or purchase price for a §423 plan) gets taxed as ordinary income, added to your W-2 in the year of sale. If you wait past both clocks, the ordinary-income piece is capped at the lesser of the offering-date discount or actual gain at sale. Everything beyond that is long-term capital gain at federal 15% or 20% plus 3.8% NIIT, instead of 32% to 37% ordinary.

Worked example: the cost of selling six months early

Example. Priya is a Cupertino-based engineering manager. She enrolled in her employer's ESPP on January 1, 2024, with a 15% discount and a six-month look-back. The stock was $180 on the offering date and $220 on the June 30, 2024 purchase date. She bought 100 shares at $153 (15% off the lower price of $180), so her per-share economic value at purchase was $220 minus $153 equals $67. Total purchase: $15,300 for shares worth $22,000.

By May 2026 the stock is at $290. She wants to sell. Both her clocks: offering date Jan 1 2024 to May 2026 is 28 months (clears 2-year test), and purchase date Jun 30 2024 to May 2026 is 22 months (clears 1-year test). Qualifying disposition.

Ordinary income piece: lesser of offering-date discount ($180 × 15% = $27) or actual gain ($290 − $153 = $137). The cap wins at $27 per share, or $2,700 ordinary. The remaining $110 per share ($11,000 total) is long-term capital gain.

At her 35% federal + 9.3% California ordinary bracket, the $2,700 costs her $1,196 in tax. The $11,000 of LTCG at 15% + 3.8% NIIT + 9.3% CA costs her $3,091. Total federal + state tax on the $13,700 of gain: $4,287, or 31.3% effective.

Now run the same numbers if she had sold in December 2024 (a disqualifying disposition). The full per-share discount measured at purchase ($220 − $153 = $67) becomes ordinary income, $6,700 total. Plus short-term capital gain on any further appreciation. At her ordinary bracket the federal + state hit on the $6,700 ordinary alone is $2,964, and that is before the appreciation piece. The qualifying-versus-disqualifying decision saved her over $2,500 on this single lot. Multiply across 8 to 12 lots over a career and the dollars get serious.

Full mechanics in our ESPP tax rules guide.

Concentrated stock: the real Cupertino risk

If 50%, 60%, 80% of your investable assets are in your employer's stock, you are running a portfolio that no fee-only advisor would ever build for you intentionally. Bay Area tech employees fall into it organically because the stock keeps appreciating and selling triggers federal capital gains plus California's 13.3% top rate. Three numbers to remember: California taxes capital gains as ordinary income at up to 13.3%, federal long-term capital gains tops out at 20% plus 3.8% Net Investment Income Tax, and a single 30% drawdown on a $4M concentrated position is $1.2M of paper loss that you would have permanently avoided with a diversified portfolio.

The tax-aware diversification levers we run for clients in this position:

For post-IPO employees and anyone past lockup expiry working through the diversification math, our post-IPO tax strategy page covers the full playbook.

Mega-backdoor Roth: the silent $40,000

The 2026 IRC §415(c) total defined contribution limit is $70,000 (or $77,500 if you are 50 or older). Your regular employee deferral limit is $23,500. Your employer's match is typically 6% to 7.5% of salary. The gap between those two numbers, often $30,000 to $40,000 per year for Cupertino tech employees, can be filled with after-tax contributions and immediately converted to Roth inside the plan.

Three requirements: (1) after-tax contributions enabled in your 401(k), (2) in-service distributions or in-plan Roth conversions allowed, and (3) IRS Form 5500 plan limit headroom. Most major Cupertino tech plans support all three but you have to opt in. Done across a 10-year career, this single move builds $400,000+ of additional Roth space that grows tax-free for the rest of your life. We audit every new client's January plan election. Read our deep dive on the mega-backdoor Roth for the step-by-step.

Moving to a no-tax state: the California sourcing trap

Texas, Nevada, Washington, Florida, and Tennessee all have no state income tax. The dream is: move there, dodge California's 13.3% top bracket, save five or six figures per year. The trap is that California Form 540NR and FTB Publication 1031 source RSU income based on workdays in California between grant and vest, not where you live when the shares hit your brokerage account.

If you have a four-year vest schedule with grants made while you lived in Cupertino, California will continue to claim a slice of every vest for the full four years even after you move. ESPP follows similar sourcing based on the offering period. A clean residency change requires: a hard move date, severing California domicile (driver's license, voter registration, primary care doctor, time-in-state under 45 days per year), and ideally timing the move so vests fall on the Nevada or Texas side of the line. We have shepherded clients through residency moves to Austin, Reno, Boise, Miami, and Park City, including handling Franchise Tax Board residency audits.

Working with us

Silicon Valley Tax is 15 minutes from Cupertino off the 280-85 corridor. Our office at 2051 Junction Ave in San Jose serves clients in Cupertino, Sunnyvale, Saratoga, Los Altos, Los Altos Hills, and West San Jose. We are open Monday through Sunday, 8am to 8pm weekdays, 8am to 6pm weekends. Most equity-comp client work runs as a flat-fee year-round retainer rather than a one-time April scramble because the planning windows are quarterly: vests in February, May, August, November; ESPP purchases in June and December; W-4 reviews in January.

What you can expect at the first meeting:

1. 30-minute working session, in office or video, no charge.
2. We review your most recent pay stub, latest brokerage statement, prior-year tax return, and equity grant summary.
3. You leave with a written summary of your withholding gap, ESPP lot status by qualifying date, and concentration ratio. Plus a flat-fee quote if it makes sense to engage.
4. No high-pressure close. Sleep on it. We will be here.

For a broader look at equity compensation work, see our tech employee tax planning page and equity compensation tax services.

Frequently asked questions

Why does my employer only withhold 22% on my RSU vests when I'm in a much higher bracket?

Federal supplemental wage withholding is a flat 22% on the first $1,000,000 of supplemental wages each calendar year (37% above that). If your marginal federal rate is 32%, 35%, or 37%, you have a withholding gap of 10 to 15 percentage points on every RSU dollar vested. For a Cupertino senior engineer with $300,000 of RSU income in a year, that gap can produce a federal underpayment of $30,000 to $45,000 by April 15. We model the gap each quarter and either adjust W-4 step 4(c) or set up estimated tax payments so you do not owe a five-figure check at filing.

What is a qualifying disposition on Apple-style ESPP, and why does it matter?

A qualifying ESPP disposition requires holding the shares more than two years from the offering date and more than one year from the purchase date. When you qualify, the ordinary income piece is capped at the lesser of (a) the discount on the offering-date price or (b) actual gain at sale. Everything else is long-term capital gain. A disqualifying sale taxes the full purchase-date discount as ordinary income, regardless of stock movement. For a 15% discount with a typical six-month look-back, the difference between qualifying and disqualifying can be 12 to 17 percentage points of effective federal rate on the discount portion. We tag every lot, track both clocks, and run the sell-versus-hold model before you click.

I have over 60% of my net worth in my employer's stock. What are the tax-efficient ways to diversify?

Four common levers: (1) sell long-term lots first and harvest losses against shorter-term gains, (2) layer in a 10b5-1 plan to sell on a schedule that satisfies trading-window rules and removes timing emotion, (3) gift highly appreciated shares to a donor-advised fund for an immediate ordinary-income deduction at fair market value with no capital gain, and (4) exchange funds (for accredited investors) that pool concentrated positions and redeem diversified after seven years with no recognition event. Each has tradeoffs around liquidity, deduction limits, and 1042 carryover. We model the after-tax return of each path against your concentration tolerance before picking.

Does my employer's 401(k) actually offer a mega-backdoor Roth?

A mega-backdoor Roth requires three plan features: after-tax contributions allowed above the regular $23,500 deferral limit (2026), in-service distributions or in-plan Roth conversions, and a total plan limit that leaves room (2026 limit is $70,000 employee plus employer combined). Most Cupertino-headquartered tech plans support all three. The mechanic is: max your pre-tax or Roth at $23,500, then contribute after-tax dollars up to the gap, then immediately convert to Roth so growth happens tax-free. Done correctly, that is $30,000 to $40,000 of extra Roth space per year. We audit your plan election each January.

I'm considering moving to Nevada or Texas to escape California tax. How does that actually work?

California taxes RSUs based on workdays in California between grant and vest. Even if you move on January 1 and never set foot in the state again, RSUs granted while you were a California resident continue to throw off California-source income on each vest until the grant is fully vested. ESPP follows similar sourcing rules based on the offering period. The play is not just changing your address. It is timing the move, accelerating or deferring vests where you have a choice, severing California domicile cleanly (driver's license, voter registration, primary doctor, time-in-state log), and being ready for a California residency audit. We have run the residency-change workflow for clients moving to Austin, Reno, Boise, and Miami.

What does it cost to work with a Cupertino tax accountant?

Individual tax preparation with RSU, ESPP, and stock activity typically runs $850 to $2,400 depending on number of brokerage accounts, equity grant complexity, and whether rental property or a side business is involved. Year-round equity planning is usually billed as a flat-fee advisory retainer of $3,000 to $7,500 per year. Initial consultations are always free. We are open seven days a week.

Ready to stop guessing on your equity comp?

If you are in Cupertino, Sunnyvale, Saratoga, or Los Altos and have been hoping the W-4 withholding is "close enough" or that ESPP timing "will sort itself out," it almost certainly will not. The dollars at stake are real and the planning windows are quarterly, not annual. Book a free 30-minute consultation with Silicon Valley Tax at (408) 383-9870 or schedule online. We will walk you through your withholding gap, your ESPP lot status, and your concentration exposure in one session. No charge, no commitment, no upsell.